This resubmitted application requests renewed NIH support for the predoctoral Columbia University Graduate Training Program in Microbiology and Immunology. Support is requested for four training grant positions each year, as per the previous cycle. Our PhD granting program provides predoctoral trainees with a unique opportunity to obtain individualized training within a broad yet cohesive program of scientific inquiry into the immune system, host response to infection, pathogen biology, systems approaches to microbiology and immunology, cancer immunology, human immunology, transplantation, and processes of microbial and immune cell replication. Extending beyond traditional boundaries that separate microbiology and immunology, our research interests converge on three cross-disciplinary themes: i) immune cell and tissue development and homeostasis, including a major emphasis on human immunology; ii) pathogen biology and host response; and iii) DNA replication and repair and their links to cell proliferation, including cancerous processes affecting the immune system. Our 23 preceptors, with primary appointments in basic science or medical departments at the Columbia University Irving Medical Center (CUIMC), demonstrate outstanding research and training records. Most preceptors are appointed to the Department of Microbiology and Immunology, which administers this program. Trainees take courses in microbiology and immunology, molecular genetics, biochemistry, cell biology, computational and quantitative biology, and responsible conduct in research. Students also enroll in workshops on scientific writing, grant preparation, and critiquing. Trainees must also pass a qualifying examination that tests their ability to formulate and defend a hypothesis-driven project. Our graduate program is led by our Director Dr. David Fidock and Associate Director Dr. Uttiya Basu. Our programmatic framework includes an Advisory Committee that regularly evaluates student and trainer performance, the curriculum, and Training Grant Eligible applicants; a mentoring plan for junior trainers; and an External Review Board comprised of three Program Directors who provide regular feedback to help optimize program effectiveness. In the six years since our Graduate Program was first awarded NIAID funding, we have consistently recruited an excellent cohort of students, with a mean GPA of 3.6 and an average of 21 months of full-time incoming research experience for our TGE entrants, who constituted 90% of our entrants. Underrepresented minorities, who we actively seek to recruit, comprised 17% of our cohort. Our program is flourishing, as evidenced by the exceptional publication record of past and current trainees. Over >95% of our graduates have remained in science or science-related fields. We also benefit from strong institutional support from our Dean and the Office of Graduate Affairs, as well as the many scientific, educational and career development resources at CUIMC. Our dynamic, rigorous and enriching graduate program is committed to training future leaders and innovators in microbiology and immunology research.